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From: Colin Percival <cperciva@FreeBSD.org>
Date: Fri, 24 Jun 2016 23:39:45 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r302184 - head/release/tools
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Author: cperciva
Date: Fri Jun 24 23:39:44 2016
New Revision: 302184
URL: https://svnweb.freebsd.org/changeset/base/302184

Log:
  Turn off MSI-X interrupt migration by default in EC2 instances; this works
  around a bug in older versions of Xen and unbreaks SR-IOV (aka. "EC2
  Enhanced Networking").
  
  Approved by:	re (gjb)
  Thanks to:	jhb, Jeremiah Lott

Modified:
  head/release/tools/ec2.conf

Modified: head/release/tools/ec2.conf
==============================================================================
--- head/release/tools/ec2.conf	Fri Jun 24 23:36:22 2016	(r302183)
+++ head/release/tools/ec2.conf	Fri Jun 24 23:39:44 2016	(r302184)
@@ -77,6 +77,12 @@ vm_extra_pre_umount() {
 	# by default for now.
 	echo 'hw.xbd.xbd_enable_indirect="0"' >> ${DESTDIR}/boot/loader.conf
 
+	# Some EC2 instances run on a version of Xen which has a bug relating
+	# to the migration of MSI-X interrupts; this is visible as SR-IOV
+	# networking (aka. "EC2 Enhanced Networking") not being able to pass
+	# packets.  Disable MSI-X interrupt migration to work around this bug.
+	echo 'machdep.disable_msix_migration="1"' >> ${DESTDIR}/boot/loader.conf
+
 	# The first time the AMI boots, the installed "first boot" scripts
 	# should be allowed to run:
 	# * ec2_configinit (download and process EC2 user-data)